Rotary pistons, in the nature of encased, eccentrically positioned rotors with radially extending vanes which move in and out of the rotors, depending upon their position on the rotational cycle of the rotor, used, for example as pumps or turbines, are known. One such device is described in U.S. Pat. No. 6,554,596 of Albert and David Patterson issued Apr. 29, 2003, in which the vane movement, in and out of the rotor, is achieved by cam surfaces within the casing which act on both inner and outer edges of the vanes.
In my co-pending U.S. patent application Ser. No. 10/680,236 entitled “Rotary Pistons”, the outward movement of the vanes is achieved by upward extensions of shoulders at the sides of each vane, which upward extensions contain pins which are seated in races continuously extending in portions of the interior wall of the casing and positioned so that as the pins move about the races, they draw their respective vanes outwardly.
Other known constructions of such vane pumps require centrifugal force, through rotation of the rotor, to force the vanes out.
Thomas Industries currently markets a rotary piston pump of the type in question, where the vanes do not move radially but instead move at angles to each other within shallow slots, each slot having a depth of less than half the diameter of the cross section of the rotor body, each vane being supported by the walls of the corresponding slot during operation of the rotor. As the slots are the support for the vanes, the vanes are permitted to extend out of the slots only a limited degree, reducing the volume of fluid that can be pumped at one time. As well, the vanes can handle only limited pressure. This pump is particularly well suited for propulsion of jet ski water craft.
Traditionally, positive displacement pumps have been of relatively complex construction and have been limited in their applications.
It is an object of the present invention to provide a positive displacement pump which is relatively economical to construct and efficient in its operation, which will be able to withstand high pressures, and which will be able to pump relatively high volumes of fluid.